Many runners who compete at successive track locations carry their own starting block assemblies with them. While the whole may be transported on the floor or in the trunk of a car, it becomes even more unwieldly when moving it by train, bus or moped. Consequently it would be desirable if the central alignment bar at least, coul be segmented so as to have its partial lengths carryable in a short handbag or placed in the carrier of a bicycle or the like. The persistant problem of course is to achieve a multiple piece assembly which is quick and readily assembled to a rigid form.